Blow molding machines conventionally provide a parison, i.e. a tube of hot plastic, between open sections of a mold. Closing of the mold then clamps the parison and allows air to be blow into the parison such that it assumes the shape of the mold. After suitable cooling has taken place, the mold sections are opened to allow ejection of the molded part.
Blow molded parts such as containers have conventionally included paper labels that are glued thereto after the molding to identify the contents of the container to the consumer. One problem is that such paper labels can become wrinkled if dampened and can also become detached from the container if a waterproof glue is not used. Also, paper labels require a separate labeling step after the molding which thus adds to the cost of the container.
In-mold labeling has been developed in the recent past to provide superior bonding of labels to blow molded plastic parts. This in-mold labeling is performed by initially inserting a label within the mold prior to the introduction of the parison and by then closing sections of the mold in preparation for the blowing operation. The subsequent blowing operation forms the parison around the label to the shape of the mold and provides a permanent bond which is incapable of being broken by moisture or otherwise. Also, such inmold labeling provides a smooth transition between the label and the adjacent surface of the molded plastic part and further provides additional strength since the label cooperates with the plastic in resisting deformation. Such strengthening also allows the use of less plastic to blow mold the part and thereby reduces the ultimate cost to the consumer. Furthermore, when utilized with containers for carbonated or other beverages, it is believed that in-mold labeling reduces the flow of carbon dioxide and other fluids through the container wall over a period of time and thereby increases the shelf life.
Prior in-mold label dispensers for blow molding machines conventionally include a label carrier having a vacuum cup that receives a label from a label magazine and is then moved to deposit the label within the mold cavity whereupon termination of a vacuum drawn at the vacuum cup allows a vacuum drawn at the mold cavity to secure the label in position in preparation for the blow molding. Such vacuum type label carriers have previously been mounted on linkages that move the labels along an angular path with respect to the direction of opening and closing movement of mold sections of the mold in order to permit depositing of the labels in the confined space permitted by the extent of the mold opening.
Another prior art type of in-mold label dispenser is disclosed by Hellmer U.S. Pat. Nos. 4,355,967 and 4,359,314 and includes a vacuum type label carrier that is moved along an abruptly curved path by a complex linkage which executes a 180 degree turn in order to transfer labels from a label magazine to the mold in preparation for molding.
Hellmer U.S. Pat. No. 4,397,625 and Boss U.S. Pat. No. 4,498,854 disclose in-mold label dispensers wherein fluid motors move vacuum type label carriers to transfer labels from label stacks to associated molds.
Slat et al U.S. Pat. Nos. 4,479,770, 4,479,771 and 4,639,207 disclose in-mold label dispensers wherein a first solid mechanical drive moves a dispensing head between inserted and withdrawn positions with respect to an open mold and wherein a second solid mechanical drive extends and retracts vacuum type carriers in order to transfer labels from a label magazine to a mold to perform the labeling operation. Use of such solid mechanical drives to move the dispensing head and the label carriers permits accurate positioning of the labels. Also, the in-mold label dispenser of the mentioned U.S. Pat. No. 4,479,771 patent provides labels to a plurality of vacuum type label carriers with a single label magazine. This is accomplished by mounting the label carriers on a dispensing head which is moved past the label magazine and paused upon alignment of each label carrier with the label magazine to permit the supply of a label to the label carrier such that all of the label carriers receive labels prior to movement of the dispensing head to an inserted position between open mold sections to transfer the labels to the mold.
Bartimes et al U.S. Pat. No. 4,479,644 discloses another type of in-mold label dispenser for use with a plastic blow molding machine wherein vacuum label carriers transfer labels from label magazines to a mold.
Ziegler U.S. Pat. No. 4,582,474 discloses an in-mold label dispenser with different embodiments capable of transferring labels from label magazines to single, dual, and three cavity molds. In certain applications, multiple cavity molds are desirable to increase production from the blow molding machine while still maintaining the same cycle time such that quality can be maintained. The in-mold label dispenser that provides labeling of single, dual, and three cavity machines in accordance with U.S. Pat. No. 4,582,474 has a carrier arm with a first end pivotally supported on a base of the dispenser for movement about a pivotal axis to move a dispensing head with a vacuum label carrier on a second end of the carrier arm along a curved path between a withdrawn position adjacent a label magazine and an inserted position between mold portions to which one or more labels is transferred. A drive mechanism of the dispenser includes a first drive that pivotally moves the carrier arm between the withdrawn and inserted positions and also includes a second drive that moves the label carrier on the dispensing head between retracted and extended positions during cyclical operation that provides the in-mold labeling.
Darr U.S. Pat. Nos. 4,585,408, 4,639,206 and 4,721,451 disclose in-mold label dispensers for plastic blow molding wherein a dispensing head with vacuum label carriers thereon is moved with rectilinear motion between a withdrawn position adjacent label magazines and an inserted position between open mold portions, and the dispensing head is also moved transverse to the direction of the rectilinear motion between an aligned position with respect to the open mold and a label transfer position to provide the inmold labeling. The in-mold label dispenser of U.S. Pat. No. 4,585,408 has an elongated support that mounts the dispensing head for the rectilinear movement and is itself mounted about a pivotal axis to support the dispensing head for pivotal movement between the aligned and label transfer positions. In the in-mold label dispenser of U.S. Pat. No. 4,639,206, a pair of locators mounted by base portions on opposite sides of the mold are engaged with each other as the dispensing head is moved to its inserted position to thereby provide support in locating the dispensing head prior to arcuate movement to the label transfer position for dispensing of labels. With both of these dispensers, arcuate movement of the dispensing head between its mold aligned and label transfer positions does not permit labeling of certain mold constructions since the degree to which the dispensing head can move arcuately is limited by the mold construction and the construction of cavity sections within the mold. In the in-mold label dispenser of U.S. Pat. No. 4,721,451, the dispensing head is moved rectilinearly between the aligned and label transfer positions in a transverse direction to the rectilinear movement between the withdrawn and inserted positions.
All of the in-mold label dispensing systems disclosed by the above mentioned patents transfer discrete sheet-like labels on one or more vacuum carriers from one or more label magazines to the mold in which the blow molding is performed with the in-mold labeling. On occasion, the vacuum carrier can pull more than one label from the magazine since the labels tend to adhere to each other to a certain extent. Spring fingers of the label magazines are designed to prevent more than one label from being transferred during each cycle, but occasionally more than one label can nevertheless be pulled from the magazine by the vacuum carrier due to the adherence of the labels to each other. This can result in a second label being placed within the mold out of the intended position as well as the one label at the correct position. Furthermore, when one label is applied to each mold portion of a mold so as to provide labels on the opposite sides of the blow molded product, malfunctioning of the dispenser mechanism associated with one mold portion can result in the blow molded product being molded with only one label rather than the required two labels. Such mislabeled products must be heated to remove the misapplied label since regrinding of the product for scrap with a label adhered thereto will produce reground resin that results in holes in the subsequently blow molded products due to the presence of the label material. However, it is nevertheless necessary to perform the label removal since government regulations, the cost of solid waste disposal of relatively bulky blow molded products, and the cost of resin will not permit economical manufacturing if the labels are not removed and the waste product reground for recycling.
In-mold labeling has also previously been performed with labels that are supplied in strips that are conveyed to the mold for the in-mold labeling such as disclosed by U.S. Patents: Battenfeld et al U.S. Pat. No. 3,287,198; Borkmann U.S. Pat. No. 3,292,209; Dickinson U.S. Pat. No. 3,324,508; and Langecker U.S. Pat. No. 3,801,689. While such strip type labels can eliminate certain problems involved with in-mold labeling, there is label scrap involved which is not economical and the molds utilized must be specially adapted to permit the label strips to be moved into position for transferring a label portion of the strip to the mold for the in-mold labeling.